Feeds to 2 Ovens and hob ?

[Blimp]

Hi Great site!!

I would appreciate some advice as above, I have:-

2 x single intergrated ovens @ 3400w
1 x induction hob @ 7200w

I already have 1 spare 32amp mcb in my cu

Could I connect the 2 ovens to a single 32amp mcb via either 1 or 2 single cables, 2.5mm?

and lastly what size cable/mcb should the hob be on ?

Thanks in advance.

 

[Taylortwocities]

The max load for 2.5mm cable is 20amps.
Your ovens will require a 16amp feed for EACH one.
The hob will require a 32amp feed (6mm cable nominally).

Dont forget that this work is notifiable under building regs part P.

You'll need to get your consumer unit extended and probably updated as the new work will need to comply with the new regulations.

IMHO not a DIY job.

 

[Steve]

IMO the two ovens could be on one 32A MCB with a bit of thought.

4mm² cable to each, from a 2 way CU with two 16A MCBs. Two isolators above the worktop.

 

[ban-all-sheds]

IMO the two ovens could be on one 32A MCB with a bit of thought.

The whole lot could be on the 32A breaker. If you believe in diversity it's 21A...

Will still need a small CU though, 3-way.

4mm² cable to each,

Why not 2.5mm²?

 

[Steve]

4mm² cable to each,

Why not 2.5mm²?

Belts and braces innit

 

[ban-all-sheds]

Do you always install your circuits using cable which is bigger than it needs to be?

Lights on 2.5mm², ring finals using 4mm², showers on 16mm².....

 

[Blimp]

hi

Thanks...

Informative & entertaining


ban-all-sheds

When you say the whole lot on 32amp did you mean the hob as-well as the 2 ovens?

 

[ban-all-sheds]

Yup.

It's a legitimate design - the assumption with cooking appliances is that you will never have everything going flat out simultaneously for long enough to trip the circuit breaker.

It's a mildly contentious topic (do a search here for 'diversity'), and personally I'd not install a 32A circuit for that load, but it's what's there already, so if it were me I'd be tempted to give it a try and see if it was OK in practice. As I said - if you imagine your separate appliances to be a dual-oven range cooker, and apply the diversity calculations you get an effective load of 21A...

 

[Taylortwocities]

Diversity is a grey area and is up to the designer.
I like to err on the side of caution otherwise you may get the situation of cold turkey on Xmas Day when both ovens and the hob may well be going full blast.

For domestic ovens the rule is to allow 10 amps plus 30% of the remainder. This is valid for a single appliance but was not designed for several appliances so I tend to apply 10 amps plus 30% for EACH appliance.

So for this situation you get:

Oven 1 (15A) = 10+ 1.5 = 11.5
Oven 2 (15A) = 10+ 1.5 = 11.5
Hob ( 31.3A) = 10+ 6.5 = 16.5

Total assumed load = 39.5amps

 

[ban-all-sheds]

Imagine that I was a skilled metal basher and welder, and that I bought that hob and those 2 ovens, and made myself a nice freestanding cabinet for them all out of stainless steel, and that I installed them and cabled them internally to a common set of terminals via which I connected the whole lot to the supply.

Can you explain why it would then use less electricity than you say the 3 components would if I hadn't made my cabinet?


Or, alternatively, if I bought a range cooker with a 7.2kW hob and two 3.4kW ovens and then dismantled it, set the hob into a worktop and put the two ovens in a tall cupboard, one above the other, can you explain why I'd then start to use more electricity?

 

[Steve]

 

[Taylortwocities]

As I said

I like to err on the side of caution

Sure, you could re-engineer it and probably, possibly, get away with it. I'd prefer to get back from the pub on Christmas lunchtime and find that everything is nice and hot.

 

[BS3036]

I'd prefer to get back from the pub on Christmas lunchtime and find that everything is nice and hot.

Reminds me of one Christmas when I was young. We got back from the pub to find that the saucepan of carrots (aluminium) wasn't there anymore. A black object lying across the element looked like it was once a carrot. Underneath in the grill area was a pool of aluminium. Didn't get carrots that year.

 

[securespark]

4mm² cable to each,

Why not 2.5mm²?

Because Steve was suggesting the two ovens could go on the 32A breaker as long as 4mm² was used. If 2.5 was used, the breaker would have to be 20A.

 

[Steve]

4mm to a local mini CU, where it splits to two 16A circuits in 2.5mm.